Travel-rating service Trip Advisor is being investigated in Italy over concerns the site is not doing enough to prevent fake reviews.

The Italian competition authority said it had had complaints from consumers and businesses about the website.

It has launched a separate investigation to see if agreements booking sites Expedia and Booking.com hold with hotels are preventing consumers from getting better deals.

Trip Advisor has defended its business.

"It is important to note that Trip Advisor fights fraud aggressively and we are confident in our systems and process," said a spokesman.

"Every single review goes through our tracking system, which maps the how, what, where and when of each review.

"Unfortunately every major service industry has to confront the challenge of fraud, but ultimately, if people didn't find the reviews on our site helpful and accurate they wouldn't keep coming back."

Expedia said it was "convinced it is acting in full compliance with all applicable laws". Booking.com has yet to comment.

Trip Advisor is a highly influential site, where a volume of positive or negative reviews can strongly affect tourism businesses.

The Italian competition authority will try to establish whether Trip Advisor has sufficient measures in place to detect reviews made by people who had not visited the place in question.

The watchdog also said it was looking at whether Trip Advisor did enough to distinguish between content submitted by travellers and posts paid for by hotels and other travel businesses.

'Limit competition'

In a separate investigation, booking websites Expedia and Booking.com are to be investigated over clauses they put in place for hotels that are listed on the sites.

"The analysis centres on clauses applied by Booking and Expedia that prevent hotels from offering better prices and conditions through other online services and, generally, any other booking system (including hotels' own websites)," the watchdog said.

"The authority believes the use of such clauses by the main two platforms on the market may significantly limit competition."

The announcement comes in the same week that Italy launched an investigation into Google, Apple, Amazon, and games publisher Gameloft over "free-to-play" games.

The watchdog said it had concerns that the games did not make it clear how much it may cost to progress in the game.

"Consumers could wrongly believe that the game is entirely free and, in any case, that they would know in advance the full costs of the game," the watchdog said.

"Moreover, insufficient information seems to be provided to consumers about the settings needed to stop or limit the purchases within the app."